1. Field of the Invention
This invention relates to a programmable logic controller provided with a private operating system that does not support the TCP/IP protocol but is adapted to automation programs and is equipped firstly with at least one intelligent module in which an HTTP server is installed, and secondly a communication module that can be connected to remote equipment through a bus.
2. Description of the Background
A modular programmable logic controller is composed of a programmable processing unit and intelligent modules that perform automation functions (for example weighing, axis control, regulation, etc.) and are connected to the processing unit through a communication bus or networks with private protocols. The hardware and software technology (real time kernel, operating system and communication protocol) of the logic controller is usually xe2x80x9cproprietaryxe2x80x9d, in other words specific to the logic controller manufacturer. The programmable processing unit contains the application written in a logic controller programming language (for example in the language known as PL7 for Schneider Automation logic controllers). An intelligent module is a microcomputer provided with a processing unit, RAM and ROM and private inputs/outputs.
Furthermore, the logic controller may be equipped with a communication module for connection to a TCP/IP type network and On/Off or analog input/output modules.
A TCP/IP communication module implements server functions (for example the HTTP server function) that enables a TCP/IP client to connect itself to the logic controller through a network under the TCP/IP protocol. Remember that a TCP/IP client is equipment that opens a connection to a TCP/IP server under its own initiative. The TCP/IP communication module may also implement a client function on TCP/IP so that it can be connected to the server TCP/IP equipment.
The TCP/IP communication module can be used as a bridge to transport frames from a network with a private protocol to a network with a TCP/IP type protocol. If the communication module is to offer services like an FTP (File Transfer Protocol) downloading server, or HTTP (Hypertext Transfer Protocol) or SNMP (Simple Network Management Protocol) agent, the system unit of the programmable logic controller makes data areas available that these various services present to remote client stations in the TCP/IP network. Client services such as xe2x80x9cmailxe2x80x9d, FTP type client, SNTP (Simple Network Time Protocol) type client, or SAP type client (client software/company management server particularly including production management functions) can enable the logic controller application program to store information output from remote servers using these protocols, in memory. Client or server functions are predefined and coded in the TCP/IP communication module. An adaptation application must be implemented in the logic controller system unit before services provided by intelligent modules are accessible from the network.
The purpose of the invention is to enable an intelligent module to host a client function or a server function or to be member of a Multicast group by using TCP/IP services provided by a communication module defining the configuration of the programmable logic controller. In this case the intelligent module can be used by a member of the TCP/IP network as if it were physically connected to it.
The logic controller according to the invention is characterized by the fact that the intelligent module is provided with an application programming interface that enables remote use of connection and communication functions of a TCP/IP type communication module.